Flooding events can be precipitated by natural and manmade inputs. These events can be particularly challenging for buildings and infrastructure located at or near a body of water. Transportation systems or buildings in these areas that are below the normal waterline are particularly vulnerable. Severe storms with high tidal surges or flash floods, rising sea levels, and seismic activity are some of the challenges posed by nature. Accidents, terrorism, and mechanical failures are manmade threats that can cause flooding, or magnify flooding from natural events.
Many subway and vehicular tunnels that operate below waterline around the world have experienced flooding. Countless buildings and structures such as power substations have also experienced flooding. Hurricane Sandy was particularly devastating to New York City in 2012 because a significant portion of the subway system was flooded and economic losses were unprecedented. Water entrance points included subway portals, stairwell entrances, ventilation shafts, emergency exits, and elevator shafts. Vehicular tunnels were also flooded, as well as many buildings. This was one of the worst flooding events in a large city in history, but it was just one in a string of events in subway systems in major cities around the world.
There are many types of flood mitigation wall systems available commercially. This includes sand bags, inflatable walls, deployable mechanical walls, and flood doors. Most of these devices are stored remotely and transported to the point of use when needed. This requires the user to have extensive logistical plans and training in place to provide effective protection. These wall systems are also labor intensive and time consuming to deploy, especially when under threat of a storm when personnel are busy with many tasks. Also, since most deployable wall systems have numerous components there is a considerable risk of difficulties from improper assembly that can result in leakage or failure of the wall. Mechanical systems such as rigid doors that are stored at point-of-use solve some of the issues with deployable wall systems but often require significant modification to the infrastructure during installation, a considerable amount of storage space for concealment, frequent maintenance, and are costly to install. They are also limited in the span of opening they are attempting to close off. Because of this, they are often found to be unacceptable in numerous applications.
Textile and membrane based flexible flood mitigation walls offer significant benefits over the existing wall devices. Most notable is the ability to pack the wall system into a small volume for point-of-use storage. This not only allows the flexible flood mitigation wall to be stored in a small volume that is compatible with space available, but it also minimizes the modifications required on the infrastructure to install it. The membrane wall itself is shaped to minimize stress in the material (governed by thin-walled pressure vessel equations, specifically pressure and radius).
The wall is deployed by first removing the cover over its storage container which is attached to a perimeter wall or building adjacent to the opening. The fabric wall, which is attached and sealed to the anchor post, is then extended and attached to the receiver post. The ground skirt is positioned against the ground and the wall is ready to retain fluid pressure. In the case of more dynamic events or when reducing leakage is critical, the skirt may be fastened under clamping bars to compress a seal and fix the base of the wall to the ground. In this case pre-installed receivers for mounting bolts are required.
In the case of longer span walls, intermediate posts can be deployed to support the wall intermittently, or preinstalled bollards can be used. Prior to deploying the fabric wall, cables may be extended between the posts to facilitate deployment by allowing the wall to deploy like a shower curtain.
When water, waves, and floating debris impact the wall, the loads are transferred from the fabric into the posts and then into the ground. The posts can be straight beams or can be buttressed for additional bending strength and control of the loading. The flexible fabric wall can be constituted of one or several layers or different types of materials to provide protection from threats of all kinds including water pressure, wave action, floating debris impact, or even chemical threats. The Extendible Flexible Flood Barrier can follow any perimeter shape with positive and negative recesses, angular changes, or grade changes. It can be continuous and completely surround a structure, or simply bridge an opening and seal against the sides of the opening via the addition to sealing materials on the posts that abut the buildings.
The Extendible Flexible Flood Barrier can also be used as a containment device that keeps a fluid inside an area and prevents its escape. This could be in the form of a deployable wall around a location where hazardous materials are used and spills are required to be contained.